sharpener

Some interesting projects under this Government scheme. Also a subsided training scheme has been announced, some details here. Apols if you knew this already, I didn't.

Happy to report that the pdf bought from UK Planning Maps passed validation by ####### District Council yesterday. The online markup for the site boundary worked OK for me after a bit of practice despite what one of the reviews says. The hard copies turned up from Kirkwall 48 hours later, not really necessary but bought as an insurance, printed on good stiff paper and not creased in transit. I edited the file to add the proposed heat pump (a tiny rectangle 3 x 9 pixels!) using IrfanView, which is a free download, to convert to .bmp and using MS Paint to edit, then the reverse. Some advice on the website on how to do this would be helpful. Conclusion: does what it says on the tin!

There's a proprietary device for doing exactly this, mentioned in the Mixergy-lite thread IIRC.

Only if it runs parallel to the first floor floor joists. My experience with plumbers is they do not know, do not understand and do not comply with the quite strict rules about holes and notching. I kept back a £500 retention until they produced a structural engineer's letter confirming that what they had done in contravention to the rules was acceptable, which never happened (they sent a span table for non-load-bearing ceiling joists which I rejected as irrelevant). Some of the £500 went on doubling the affected joists which I did myself. The prime contractor was a loft conversion firm, and when a neighbour saw their site board outside he told me he had won a court case against them for £50k damages so I had got off lightly. Later they went bust - for a second time. I did not feel very guilty.

So "primary circulation" (rule b) seems to trump the "1 metre" bit (rule c). All qualified by "In a new system". Does an old hw system incorporated into a new HP system become "new" or not @JamesPa ? Personally I don't care about pipes that are within the thermal envelope, especially where they pass through the airing cupboard.

From data sheets it seems for a given frame size they differ only in refrigerant charge, software and possibly max compressor, fan and pump revs. Hence it would seem entirely possible to downrate a unit once installed if it proves to be too big, does anyone offer that as a feature?

Fitting their fancy tracker will not help much, the toerags will quickly learn to recognise them, remove them and leave them on site behind a bush. A spair pair in one of the interconnection cables could however easily be linked to a wired or wireless burglar alarm and it will then alert the entire neighbourhood at the time if the wires are disconnected or cut. Better still one core in each of two cables. And/or linked to microswitches on the covers and inside the mains isolator.

MCS guidance here, you will see they suggest a bigger HP can get away with a smaller cyl because of greater reheat capacity, not seen this on cyl mfrs web sites (try googling hot water tank sizing, you can choose any answer you like over a wide range!). Conversely if you are trying to minimise the HP size then a bigger tank will help avoid the need to reheat it when space heating is required. With the solar thermal as well you might be able to heat only at off-peak times. 3 sq m surface area will be fine with a 5-7 kW HP. Makes a lot of sense.

Surely they would not add the mechanical complication unless it was necessary for some performance reason like achieving a reasonable turndown ratio - which may still be uncompetitive so they don't publish it. Hopefully @markocosic will be along to tell us, if he is not on holiday.

"they" is Samsung re the OP, Good Energy quotes are based on Midea FWIW so I imagine they are not rubbish.

PV since that is what I have but could of course be either like @embra in the other thread

Sounds a retrograde step! Will he not just add a plate heat exchanger to the exisiting setup? Or at least keep the solar tank as a preheater if you have the space. Our installer wants to put in a new 300 l tank for 4 bedrooms, saying this is required for an occupancy of 5 people which he gets from some table calling for [#bedrooms +1] so if this is correct you would need 300 also as @ProDave suggests - but I have not given up on the heat exchanger approach. Assuming reasonable insulation the HP will only be called upon to replace the HW actually drawn off, so if your usage pattern does not change then an increase in tank capacity does not matter to the HP as it will not necessarily being heating from cold.

There is full performance data here, it seems not to be available on English-language web sites but is easy enough to work out. Your experience is similar to mine, installers play safe and make conservative assumptions as do Vaillant tech support. Watch out for lower than necessary OAT (Outside Air Temperature) assumptions, they should vary by region, the table is on p10 here. Also if you have additional heat sources e.g. WBS (Wood Burning Stove), AGA, MVHR (Mechanical Ventilation and Heat Recovery) make sure they know these are available to help out below the design OAT. Equally supplementary water heating by solar PV. These considerations are not officially allowed by MCS but might tip the balance of thinking. Arotherm + specs seem to be quite generous so you may well be right and could get away with a smaller unit. I was orginally told their 12kW was too small but after arguing that the proposed 15kW Stiebel Eltron was physically too large they reworked the figures based on 18C everywhere (?) and conceded the Vaillant would do the job. They also proposed to put lever valves in so an inline heater could if necessary be installed in the light of experience over the first winter.

IIRC @markocosic says they achieve their turn-down ratio by using hot gas bypass which knackers the CoP.

Grant and CoolEnergy can be interfaced quite easily to an existing S-Plan system as they accept external contact closures as inputs. But they are both R32 and I would prefer R290, Grant are bringing one out next year (also made by Chofu).

Various, e.g. lack of North arrow, no scale bar, no copyright licence, cba to put all that in when I could download one said to be compliant as per link above for under £20. Remains to be seen if it will pass muster, I will post back here either way.

But you also want a low unit price. Adding say a further 50mm acoustic insulation inside the casing all round would cost more and the unit would also be 100mm deeper front-to-back. I for one would rather take remedial measures elsewhere on the site. In time the best acoustic design ideas will percolate down to the cheaper models but I don't think you will ever get >10 kW HPs to be completely quiet, they have been trying this with aircon and cooling towers for decades but the physics are against you.

There is a Quiet Mark scheme already, here. But I don't think you can simplify the issue to any go/no go certification scheme as an underlying problem is the wide range of sizes of HP available, another is the different shapes of the unit. This results in a "horses for courses" situation. So for example the Stiebel Eltron 15kW has a single very large fan and a lot of soundproofing inside the case, it is does not have the Quiet Mark but is in fact 5dB quieter than the 12kW Vaillant which has two smaller faster fans and a tall slimline form factor. Either will require a screen between it and my neighbour's window to meet the MCS limit, but for the Vaillant it needs to be a bit bigger as full screening wins back the 5dB difference. However the tall thin unit is preferable for me as I have only a narrow yard to put it in. Whether a fence panel will in actuality give a 10dB reduction in sound power seems unlikely to me, but the MCS process is (thankfully) based on visual lines of sight alone.

ATM I have an oil boiler. As mentioned elsethread I am still trying to agree a spec with >0 HP installers, and in any case am waiting for my planning application to be validated. So posts about the control of an HP based system are purely conjectural at this stage. I agree with the received wisdom to run on WC using the TRVs only as high temp backstop limit and as zone valves for rooms that are out of use (don't start!) But I also hope to have a thermal store which I plan to heat to 55C at the same times as the HW cyl is heating, this should act as a big heat sink and avoid the HP short cycling with the (small) coil, so avoiding the need to change the cylinder. I calculate that heating the TS to 55 off-peak will still be cheaper than running the HP on weather comp at peak rate. And if there is surplus PV it will be entirely free and a good way to store the energy which would otherwise be exported to the grid without any recompense.

The electronic TRVs that are part of the Honeywell Evohome system do that also. As the room temperature approaches the setpoint you can hear the motorised valves making small adjustments to turn the flow down so there is no overshoot. The main problem with it as a system is that they use a proprietary ?460MHz? signalling protocol so it will not interface with Zigbee or any of the other open standards. And they designed it with no ability to add repeaters so it is very stretched to cover a biggish house with thick stone walls.

After a day or two with acid rainwater in it it will be clean as a whistle.

I proposed doing this and was met with a flat refusal on grounds of hygiene. Yes, mine are commoned somewhere above ceiling level, haven't yet investigated further. But the DHW coil flow pipe might well be sufficient as there is a separate CW feed in the utility room to pressurise the existing CH circuit. Not sure if it is 22mm though, mains pressure is well adequate for 15mm but not entirely confident about the rainwater supply.

I hope that now given a link with details even as to the chip family used for cell balancing you will concede they do have it.

Well yes, that would work, do you have a schematic in mind? I want to charge the TS during E7 and discharge 0700 - 0800. I think however you have no longer got the efficiency gain from running the HP at a lower temp if you are charging the TS at high temp and mixing it down. Either with the fancy mixing station at £800 or the existing blending valve on the UFH. Which is also why I plan on not having the UFH going when I am charging the TS. If I go for a TS then once I have got it up to say 55C there is no benfit in tempering to any less and I will get faster warmup by supplying the rads at the max temp, the TRVs will limit the heat input to the rooms and hence the overall heat demand according to the weather.

There were some stories on here about Daikin consuming serious power when off. I looked into this and there is a bit in the installation instructions about needing to keep the compressor heated to ?5C or it will not start when required. Last I heard from their "recommended" installer was a cryptic "I will be in touch" >two weeks ago so I have in practice given up on them.